面向对象中的session版的购物车

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先设置一个product类，用来存储和获取数据，使用LIst集合存储所有商品即（ProductDao类），在ShowProductServlet类查看商品信息，然后将数据提交到AddCarServlet类来处理数据，最后在ShowCarServlet类查看购物车并显示数量和价格。

程序运行如下图所示：

ShowProductServlet类显示效果

ShowCarServlet类查看购物车

源代码如下:

Product

package star.july.buycar;public class Product {private int id;private String name;private int price;public void setPrice(int price) {this.price = price;}private String descr;private int num =1;//默认值public int getId() {return id;}public void setId(int id) {this.id = id;}public String getName() {return name;}public void setName(String name) {this.name = name;}public String getDescr() {return descr;}public void setDescr(String descr) {this.descr = descr;}public int getNum() {return num;}public void setNum(int num) {this.num = num;}public int getPrice(){return price;}public Product(int id, String name, int price, String descr) {super();this.id = id;this.name = name;this.price = price;this.descr = descr;}public Product() {super();}}

ProductDao:

package star.july.buycar;import java.util.ArrayList;import java.util.List;//商品dao类public class ProductDao {//存储所有的商品的集合public static List<Product> data = new ArrayList<Product>();static{data.add(new Product(1,"三星",4500,"Android机皇"));data.add(new Product(2,"苹果",5800,"ISO系统，流畅爽快"));data.add(new Product(3,"小米",1999,"为发烧而生"));data.add(new Product(4,"华为",2888,"强大的研发实力"));data.add(new Product(5,"一加",1999,"超高的性价比"));}//返回所有的商品数据public List<Product> findAll(){return data;}//根据id查找商品public Product findById(int id){for(Product p:data){if(p.getId() == id){return p;}}return null;}}

ShowProductServlet:

package star.july.buycar;import java.io.IOException;import java.io.PrintWriter;import java.util.List;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public class ShowProductServlet extends HttpServlet {ProductDao dao = new ProductDao(); public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {List<Product> product = dao.findAll();//返回Product对象 //显示中文response.setContentType("text/html;charset=utf-8");//显示商品列表String html ="";html += "<html><body>";html +="<table border='1' width = 500px>";html += "<tr><th>编号</th><th>品牌</th><th>价格</th><th>描述</th><th>购买</th>";for(Product p: product){html += "<tr><td>"+p.getId()+"</td><td>"+p.getName()+"</td>" +"<td>"+p.getPrice()+"</td><td>"+p.getDescr()+"</td>" +//getContextPath：获取父目录。 在超链接中传递商品的id，用以添加商品数量"<td><a href='"+request.getContextPath()+"/AddCarServlet?id="+p.getId()+"'>购买</a></td>";   } html += "</table>";html += "</body></html>";response.getWriter().write(html);} public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException { }}

AddCarServlet:

package star.july.buycar;import java.io.IOException;import java.util.HashMap;import java.util.Map;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpSession;public class AddCarServlet extends HttpServlet {ProductDao dao = new ProductDao(); public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {//获得IDString id = request.getParameter("id");//查找商品Product product = dao.findById(Integer.parseInt(id)); //获取sessionHttpSession session = request.getSession();//设计一个集合用以存储购物车中的所有商品数据//使用session.getAttribute()是为了判断第一个商品Map<Integer,Product> car = (Map<Integer, Product>) session.getAttribute("car");//如果是第一个商品，就进行初始化if(car == null ){car = new HashMap<Integer,Product>();}if(car != null && car.containsKey(Integer.parseInt(id))){  //判断是否是集合里的key的值 Product p = car.get(Integer.parseInt(id)); //返回key（id）对应的值p.setNum(p.getNum()+1);//商品数量+1}else{//没有买过，需要重新加入购物车car.put(product.getId(), product);}//将car的值赋值给属性car，后者给前者session.setAttribute("car", car); //回显response.setContentType("text/html;charset=utf-8");response.getWriter().write(product.getName()+"已成功加入购物车！ <a href = '"+request.getContextPath()+"/ShowCarServlet'>查看购物车</a>");} public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}

ShowCarServlet:

package star.july.buycar;import java.io.IOException;import java.util.Map;import java.util.Map.Entry;import javax.servlet.ServletException;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import javax.servlet.http.HttpSession;public class ShowCarServlet extends HttpServlet { public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {//从HttpSession中取出数据HttpSession session = request.getSession();Map<Integer,Product> car =(Map<Integer,Product>)session.getAttribute("car");//显示中文response.setContentType("text/html;charset=utf-8");String html ="";html += "<html><body>";html +="<table border='1' width = 500px>";html += "<tr><th>编号</th><th>品牌</th><th>价格</th><th>数量</th><th>描述</th><th>小计</th>";double totalProduct = 0;//商品的总价for(Entry<Integer,Product> entry : car.entrySet()){Product p = entry.getValue(); html += "<tr><td>"+p.getId()+"</td><td>"+p.getName()+"</td>" +"<td>"+p.getPrice()+"元</td><td>"+p.getNum()+"</td><td>"+p.getDescr()+"" +"</td><td>"+p.getPrice()*p.getNum()+"元</td>";totalProduct += p.getPrice()*p.getNum();} html += "<tr><td colspan ='6' align='right'>合计："+totalProduct+"元</td></tr>";html += "</table>";html += "<p><a href='"+request.getContextPath()+"/ShowProductServlet'>继续购物</a>";html += "</body></html>";response.getWriter().write(html);} public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException { doGet(request, response);}}

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